Compartmented trays, sometimes called "lugs" usually made from a single blank of corrugated fiberboard, are widely used for carrying a plurality of baskets of fragile and perishable commodities such as fruit. For example, strawberries are packed in pint or quart baskets made of wood or molded plastic which are in turn placed in groups in trays or lugs of the type here involved for distribution to the trade. A typical tray is rectangular with two open top compartments each holding a half-dozen pint baskets the contents of which will lie below the top surface of the tray to permit stacking of trays without damage to the contents. Also, conventionally, the trays have numerous strategically located openings to provide air circulation to the contents when the trays are stacked for shipment or are on individual display for retail sale.
While dividers for compartmented trays of this general type have been developed and the problem of bulging or sagging of the bottom panels has been recognized in the prior art, it does not appear that the prior art affords a connection between a divider and the bottom panel which includes adhesive joints lying in vertical planes and which thus take advantage of the superior strength exhibited by such joints when subjected primarily to shear stresses instead of tension or peeling stresses.
U.S. Pat. No. 2,744,675 discloses a tray of the general type here involved wherein a divider is formed from two flaps hinged together along a crease line to provide a hollow divider of triangular cross-section. The flaps are provided with feet which snap into slots in the bottom panel. There is no provision for support of the bottom panel by interconnection with the divider and infolding triangular gussets are relied upon to assist in holding the divider flaps in position.
U.S. Pat. No. 3,055,572 is similar to the preceding patent but provides friction holding flaps which wipe across the surface of the bottom panel to assist in holding the feet in the slots in the bottom panel. While it is not suggested in this patent, it might occur to one skilled in the art to adhesively secure the friction holding flaps to the upper surface of the bottom panel. However, such adhesive joints would be subjected to stress in the peeling direction when the bottom panel tends to bulge or sag. Furthermore, adhesive placed upon these flaps would be smeared across the bottom panel when the tray is erected causing a messy finished product, loss of glue at the joint where it is needed and impairment of bonding strength.
U.S. Pat. No. 3,127,086 is a further development of the patents described above in which glue flaps extend through an opening in the bottom panel and are glued to the underside of that panel. These would tend to prevent bulging or sagging of the bottom panel away from the divider but at least a substantial amount of the stresses placed on the adhesive joint in resisting such action are tension stresses in the peeling direction.
U.S. Pat. No. 3,194,472 also discloses glue flaps on the outside surface of the bottom panel and again the stresses placed on the adhesive joint are largely in the peeling direction.
U.S. Pat. No. 4,018,377 is a further development on the type of tray here involved. In this patent the divider is provided with a horizontal top panel along which the divider flaps are folded downwardly. Glue flaps on the bottom edges of the vertical divider flaps are bent inwardly to abut and form a generally rectangular cross-section of the divider. The glue flaps are adhesively secured to the inner, or upper, surface of the bottom panel and would resist bulging or sagging of the bottom. Again, however, the adhesive joints are subjected to peeling stresses in resisting such action and, in practice, adhesive is smeared on the surface of the bottom when the joints are formed because the glue flaps on the divider flaps result in "flaps on flaps" which are difficult to control in a high speed box erecting operation, and the glue is "flicked off" when the flaps and tabs are turned down into final position.